With the rapid development of biotechnology, genetic engineering technology has provided a new approach for supply of human food and animal feed. Presently, most of the projects of genetically modified plants worldwide, which have been commercialized and are under study, are in association with food and feed, in which mature techniques have been developed for a totality of dozens of varieties, hundreds of lines, mainly including soybean, maize, rapeseed, potato, tomato, wheat and the like. Maize is one of the important food crops in the world, and the hazards faced during its process of growth are primarily from disease and insect pests, secondly from weeds. According to statistics, not spraying pesticide to maize may lead to 59% of production loss. Therefore, the earliest application of genetic engineering technology in maize is to develop genetically modified maize lines having insect-resistant and herbicide-resistant characteristics. The number of genetically modified maize lines registered in the Organization for Economic Cooperation and Development (OECD) in 2000 was 18 in total, of which improved properties were insect-resistance and herbicide-tolerance etc. In 2000, among all of the genetically modified maize cultivated in the United States, 72% were of insect-resistant characteristic, 24% were of herbicide-tolerant characteristic, whereas 4% were of insect-resistant and herbicide-tolerant characteristics in both.
Genetically modified maize BT11 is a line having simultaneously both insect-resistant and herbicide-tolerant characteristics. The insect-resistant gene transferred in it is the insect-resistant gene CrylAb of the series of BT toxic protein gene and the Glufosinate herbicide-tolerant gene transferred is Glufosinate acetyl transferase gene.
As great quantities of genetically modified crops are entering the market progressively, the safety issues of genetically modified crops and food processed from genetically modified crops have begun to be concerned by people. Essentially, there is no difference between the genetically modified crop varieties and conventionally bred crop varieties. Conventional breeding is generally realized through sexual hybridization, whereas the plant genetic engineering is to introduce exogenous recombinant DNA to the plant genome by using the techniques of agrobacteria, gene gun, Electroporation and microinjection and so on. Although theoretically speaking, the genetic characteristic and phenotype of the transferred gene may be predicted more precisely with a safer application, it is necessary at all to conduct safety assessment on genetically modified crops yet.
The European Union is the first to put forward conducting labeling administration for genetically modified food. In 1999, the non-genetically modified organisms exported to the European Union were required that should not contain pollution of more than 1% of genetically modified food; in 2002, the minimal labeling limitation was decreased to 0.9% by the European Union. Different minimal content of genetically modified component were prescribed in Japan, Australian and New Zealand, with different thresholds in the range from 1% to 5%.
In China, “Biosafety Administration Regulations on Agricultural Genetically modified Organisms” was issued and implemented on May 9, 2001, three follow-up management regulations for biosafety evaluation, labeling administration and safety administration on imported products for agricultural genetically modified organisms were issued on Jan. 5, 2002, which determined the first list of agricultural genetically modified organisms applied labeling administration, and were formally coming into force from Mar. 20, 2002.
At present, the detection of genetically modified crops mostly includes two approaches: the first, to detect whether exogenous genes (DNA) are contained. This approach mainly bases on PCR technology and hybridizing test technology of nucleic acid probes which can detect whether exogenous genes (including target genes, label genes and primers) are contained in the GMC precisely and rapidly; the second is to detect if there is exogenous protein (the product of gene expression), and this approach mainly adopts the methods of chemical analysis, gel electrophoresis and enzyme linked immunity with a comparably detailed and complicated detection work. Among these approaches, PCR detection methods are principal methods for detection of genetically modified crops, including Qualitative PCR method, Multiplex PCR method, Nested PCR method, Competitive Quantitative PCR method, Fluorescence Quantitative PCR method and the like. The Qualitative PCR and Real-Time Quantitative PCR detection methods are popularized and employed at home and abroad.
The general detection procedure of PCR amplification technique is as follows: the extraction of plant genome DNA→PCR amplification→enzymatic cleavage experiment→detection of target gene→detection report. Major apparatuses and equipments for detection are PCR equipment, electrophoresis apparatus, frozen centrifuge, Ultraviolet observing (or imaging) equipment etc. In addition, the technical conditions required for detection of genetically modified organisms are comparatively high, the apparatuses and equipments are relatively costly, as well as the cost and fee of detection are quite high.